裂纹尖端压缩应力对闭合和扩展特性影响的数值模拟

In order to study plasticity-induced crack closure (PICC) effect of FGH97 powder metallurgy superalloy, crack propagation and PICC effect of FGH97 compact tension specimen were analyzed by finite element method (FEM). The effects of element size around crack tip, constitutive model and number of cycles between each node release on crack closure ratio were examined, and the concepts of corrected crack closure ratio and corrected effective stress intensity factor range were proposed, crack propagation life was predicted and compared with test results. The results show that crack closure ratio rises until convergence with refinement of element size around crack tip from 40μm to 3μm. Crack closure ratio of isotropic hardening model is about 0.51, the value of kinematic hardening model is about 0.44, and for Chaboche model crack closure ratio is about 0.48, the value of crack closure ratio can be reflected by the size of crack tip compressive stress zone. The size of crack tip compressive stress zone and crack closure ratio tend to decrease when the number of cycles between each node release increases. The results of crack propagation tests show that the error between predicted life based on corrected effective stress intensity factor range and test life is 3.86%.